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406
METALLUEGT OF IRON AND STEEL.
The figures on the iron bars show that the situation is no better than with steel, for the welded bars are far inferior to the natural piece both in strength and ductility. These experiments are corroborated by Table XIX-B, which gives a series of tests made by the Eoyal Prussian Testing Institute.* The average strength of the
TABLE XIX-B. Welding Tests by the Eoyal Prussian Testing Institute.
Kind of metal.	tilt, strength; pounds per square inch.		Per cent, elongation in 200 m. m. =7.87 inches.		Per cent, reduction of area.	
	0-g	oT ta-d	r. 6 tests, Latural.	. 9 tests, relded.	||	'. 9 tests, relded.
	!fl	5		4	$jrt	4
Medium O. H. steel  .... Soft O. H. steel .......	72110 64670 67890	41820 45800 47080	20.8 25.1 22.2	8.2 v 6.1 7.7	84.9 44.7 89.5	4.5 10.5 14.0
Puddled iron ...... ; .						
welded bars of medium steel was 58 per cent, of the natural, the poorest bar showing only 23 per cent. In the softer steel the average was 71 per cent, and the poorest 33 per cent., while in the puddled iron the average was 81 per.cent, and the poorest 62 per cent. Complete destruction of ductility is shown in the case of all three metals.
As above stated, the flat bars in T'able XIX-A were such as had been used successfully: in making pipe which would stand all ordinary tests of distortion, while the soft basic metal would'meet the most severe tests. Such metal is used regularly where the best welding qualities are required, and the users are convinced that "the weld is perfect." It must be acknowledged that a weld as performed by ordinary blacksmiths, whether on iron or steel, is not nearly as good as the rest of the bar; and it is still more certain that welds of large rods of common forging steel are unreliable and should not be employed in structural work. Electric methods do not offer a solution of the problem, for the metal is heated beyond the critical temperature of crystallization, and only by heavy reductions under the hammer or press can much be done toward restoring ihe ductility of the piece. In many cases this subsequent hammering is impracticable.
* Journal I, and 8, J.,Vol. 1,1883, p. 425, et seq.